1. Field of the Invention
This invention relates to cooling of buildings, particularly to cooling by efficient absorption and removal of heat from solar energy from the outer surfaces of buildings, thereby obviating the necessity of expensive and energy-wasting systems for removing such energy.
2. Description of the Prior Art
The desire and need to provide cooling for buildings and structures is as old as the art of constructing human habitation. We perceive "comfort" over a very narrow temperature range. Below about 18.35 degrees Celsius, the average person has the perception of cold. Above about 26.67 degrees Celsius the average person feels uncomfortably warm. From the very beginning, the concept of a habitable structure involved providing protection from the elements, including natural temperature variations beyond that which is comfortable.
From the earliest use of mud and leaves as insulation, humans have sought to perfect the environment by the use of habitats. For much of the time, the consumption of resources, and the use of power was secondary to the achievement of a controlled environment. The prior art clearly shows the desire for achievement of control, without significant consideration for the efficient use of resources.
The prior art is replete with examples of means and devices to control, or improve on, the control of a building's environment.
U.S. Pat. No. 2,266,321 to Holder (Dec. 16, 1941), addresses the "prevention of excessive heat accumulation in exposed surfaces such as roofs." Importantly, Holder recognizes that evaporative cooling efficiently removes energy, while the excessive application of fluid on the surface decreases the effect. In a previous U.S. Pat. No. 2,069,150, (xx-date) Holder described a piping and spray system using a continuously applied spray of water. By first describing a continuous water spray, then adding an interrupted spray, Holder improved upon a basic concept of using water for cooling purposes. Holder, while envisioning a thermostatically controlled valve to interrupt the flow of water, fails to contemplate the consequences of his own analysis.
Holder correctly describes the "initially high roof cooling efficiency" as water is initially applied to the roof surface. He then continues; "the action progressively and rapidly approaches the condition of low evaporative cooling efficiency wherein main reliance must necessarily be placed upon the cooling effect of the water per se." Holder then proceeds to describe a process wherein a valve is thermostatically controlled for the application of water to the roof. Unrecognized is the effect of pooled water, rising to the temperature that is required to turn the valve on, thereby applying more water on water. This is an effect already recognized as undesirable. Holder fails to assure that water is applied without the possibility of accumulating water on the surface. Under such condition, the accumulated water may not provide any cooling.
U.S. Pat. No. 2,506,936, to Murray (May 9, 1950) continues the refinement of the cooling process by first reiterating the correct statement; "If only a small amount of water is placed on the roof, the evaporation is highly accelerated as compared to what would be if the roof surface were flooded with water." Murray's solution is the addition of a time delay after a first application of water, until the next succeeding application of water. At this point, the concept fails in several respects. First, Murray describes a means of cooling the thermostat as water is applied to the roof If the thermostat is cooled by application of too great flow of water, the roof receives to little water. If the thermostat is too cooled by too little water, the roof receives too much water. In this procedure, the surface to be cooled is not directly sensed for the correct amount of water to achieve optimal cooling.
Some early concepts utilize novel, and highly inefficient means to reduce roof temperatures.
U.S. Pat. No. 1,808,829, to Barnes (Jun. 9, 1931), describes a water-absorbent material, such as burlap or canvas, soaked with water, to act as a barrier to the sun's energy. The potential for rot and mildew, as well as other technical difficulties, make this concept unacceptable for modern use.
U.S. Pat. No. 2,660,863, to Gerhart (Dec. 1, 1953), utilizes a porous hose to effectively drip-irrigate the roof. As in Barnes, the potential for rot and mildew precludes use of this concept.
U.S. Pat. No. 4,761,965, to Viner (Aug. 9, 1988) describes a very specific arrangement of an evaporative roof cooling system. Viner describes a "plurality of water distribution . . . nozzles, a "conduit means", a solenoid valve, and a "temperature measurement means comprising a thermistor". Viner, like his predecessors, espouses the need to apply water in a thin film, allow it to evaporate, then repeat the application. Also like his predecessors, Viner falls into the trap of presuming that a timed cycle of water on/ water off will achieve the goal of optimum application of water. This timed sequence will never account for the variations in temperatures, variations of the water absorption of the roof material, variation in relative humidity, wind factor, as well as other factors that impact not only the rate of cooling of the roof, but also the rate of evaporation. Consequently, Viner fails in his goal to apply an optimally thin film of water.
Viner boasts "electrical power usage for the system is essentially zero", but describes an electrically operated solenoid control valve, and rated for continuous duty. Viner neglects the power requirements of the valve, in addition to the costs associated with wiring the valve and control systems to the building wiring.
U.S. Pat. No. 3,861,624, to Lear (Jan. 21, 1975), describes an aircraft cabin comfort control system. Lear utilizes aircraft skin temperature to regulate the flow of conditioned air to the occupants of the aircraft. Lear utilizes the temperature of the aircraft to provide a control decision for temperature regulation.
None of the prior art, from Barnes (1931) through Viner (1988), takes into account the energy absorption of generally east-facing or west-facing vertical walls of a structure, another major source of heat energy resulting in the heating of a building. None of the prior art moves beyond the concept of either timed application of water, or application of water based on surface temperature, neither being a true means of assuring that full and complete evaporation is achieved.